On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ∼ 1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40 − 8 + 8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 M ⊙ . An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ∼ 40 Mpc ) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ∼ 9 and ∼ 16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.

We present the COSMOS2015 a catalog which contains precise photometric redshifts and stellar masses for more than half a million objects over the 2deg 2 COSMOS field. Including new Y JHK s images from the UltraVISTA-DR2 survey, Y -band from Subaru/Hyper-Suprime-Cam and infrared data from the Spitzer Large Area Survey with the Hyper-Suprime-Cam Spitzer legacy program, this near-infraredselected catalog is highly optimized for the study of galaxy evolution and environments in the early Universe. To maximise catalog completeness for bluer objects and at higher redshifts, objects have been detected on a χ 2 sum of the Y JHK s and z ++ images. The catalog contains ∼ 6 × 10 5 objects in the 1.5 deg 2 UltraVISTA-DR2 region, and ∼ 1.5 × 10 5 objects are detected in the "ultra-deep stripes" (0.62 deg 2 ) at K s ≤ 24.7 (3σ, 3 , AB magnitude). Through a comparison with the zCOSMOSbright spectroscopic redshifts, we measure a photometric redshift precision of σ ∆z/(1+zs) = 0.007 and a catastrophic failure fraction of η = 0.5%. At 3 < z < 6, using the unique database of spectroscopic redshifts in COSMOS, we find σ ∆z/(1+zs) = 0.021 and η = 13.2%. The deepest regions reach a 90% completeness limit of 10 10 M to z = 4. Detailed comparisons of the color distributions, number counts, and clustering show excellent agreement with the literature in the same mass ranges. COSMOS2015 represents a unique, publicly available, valuable resource with which to investigate the evolution of galaxies within their environment back to the earliest stages of the history of the Universe. The COSMOS2015 catalog is distributed via anonymous ftp b and through the usual astronomical archive systems (CDS, ESO, IRSA).

We present measurements of the stellar mass functions (SMFs) of star-forming and quiescent galaxies to z = 4 using a sample of 95 675 galaxies in the COSMOS/UltraVISTA field. Sources have been selected from the DR1 UltraVISTA K s -band imaging which covers a unique combination of a wide area (1.62 deg 2 ), to a significant depth (K s,tot = 23.4, 90% completeness). The SMFs of the combined population are in good agreement with previous measurements and show that the stellar mass density of the universe was only 50%, 10% and 1% of its current value at z ∼ 0.75, 2.0, and 3.5, respectively. The quiescent population drives most of the overall growth, with the stellar mass density of these galaxies increasing as ρ star ∝ (1 + z) −4.7±0.4 since z = 3.5, whereas the mass density of star-forming galaxies increases as ρ star ∝ (1 + z) −2.3±0.2 . At z > 2.5, star-forming galaxies dominate the total SMF at all stellar masses, although a nonzero population of quiescent galaxies persists to z = 4. Comparisons of the K s -selected star-forming galaxy SMFs to UV-selected SMFs at 2.5 < z < 4 show reasonable agreement and suggests UV-selected samples are representative of the majority of the stellar mass density at z > 3.5. We estimate the average mass growth of individual galaxies by selecting galaxies at fixed cumulative number density. The average galaxy with Log(M * /M ⊙ ) = 11.5 at z = 0.3 has grown in mass by only 0.2 dex (0.3 dex) since z = 2.0(3.5), whereas those with Log(M * /M ⊙ ) = 10.5 have grown by > 1.0 dex since z = 2. At z < 2, the time derivatives of the mass growth are always larger for lower-mass galaxies, which demonstrates that the mass growth in galaxies since that redshift is mass-dependent and primarily bottom-up. Lastly, we examine potential sources of systematic uncertainties on the SMFs and find that those from photo-z templates, SPS modeling, and the definition of quiescent galaxies dominate the total error budget in the SMFs.

We estimate the galaxy stellar mass function and stellar mass density for star-forming and quiescent galaxies with 0.2 < z < 4. We construct a large, deep (K s < 24) sample of 220 000 galaxies selected using the new UltraVISTA DR1 data release. Our analysis is based on precise 30-band photometric redshifts. By comparing these photometric redshifts with 10,800 spectroscopic redshifts from the zCOSMOS bright and faint surveys, we find a precision of σ Δz/(1+z) = 0.008 at i + < 22.5 and σ Δz/(1+z) = 0.03 at 1.5 < z < 4. We derive the stellar mass function and correct for the Eddington bias. We find a mass-dependent evolution of the global and starforming populations, with the low-mass end of the mass functions evolving more rapidly than the high-mass end. This mass-dependent evolution is a direct consequence of the star formation being "quenched" in galaxies more massive than M 10 10.7−10.9 M . For the mass function of the quiescent galaxies, we do not find any significant evolution of the high-mass end at z < 1; however we observe a clear flattening of the faint-end slope. From z ∼ 3 to z ∼ 1, the density of quiescent galaxies increases over the entire mass range. Their comoving stellar mass density increases by 1.6 dex between z ∼ 3 and z ∼ 1 and by less than 0.2 dex at z < 1. We infer the star formation history from the mass density evolution. This inferred star formation history is in excellent agreement with instantaneous star formation rate measurements at z < 1.5, while we find differences of 0.2 dex at z > 1.5 consistent with the expected uncertainties. We also develop a new method to infer the specific star formation rate from the mass function of star-forming galaxies. We find that the specific star formation rate of 10 10−10.5 M galaxies increases continuously in the redshift range 1 < z < 4. Finally, we compare our results with a semi-analytical model and find that these models overestimate the density of low mass quiescent galaxies by an order of magnitude, while the density of low-mass star-forming galaxies is successfully reproduced.Key words. galaxies: distances and redshifts -galaxies: evolution -galaxies: formation -galaxies: star formationgalaxies: stellar content Based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under ESO programme ID 179.A-2005 and on data products produced by TERAPIX and the Cambridge Astronomy Survey Unit on behalf of the UltraVISTA consortium.Catalogues are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via

In this paper we describe the first data release of the UltraVISTA near-infrared imaging survey of the COSMOS field. We summarise the key goals and design of the survey and provide a detailed description of our data reduction techniques. We provide stacked, skysubtracted images in Y JHK s and narrow-band filters constructed from data collected during the first year of UltraVISTA observations. Our stacked images reach 5σ AB depths in an aperture of 2 diameter of ∼25 in Y and ∼24 in JHK s bands and all have subarcsecond seeing. To this 5σ limit, our K s catalogue contains 216 268 sources. We carry out a series of quality assessment tests on our images and catalogues, comparing our stacks with existing catalogues. The 1σ astrometric rms in both directions for stars selected with 17.0 < K s (AB) <